It is widely acknowledged that heat is produced during operations of electronic devices such as central processing units (CPUs). The heat produced must be quickly removed to ensure the CPUs working normally. Typically, a heatheat sink to a CPU, especially nowadays the heat sink being made heavier and heavier aiming to obtain a high heat dissipating capacity.
In earlier times, linear-type locking devices were widely used for securing of heat sinks. A linear-type locking device, which is integrally made from a resilient metal wire, generally includes an elongated central pressing portion and a pair of locking arms extending from opposite ends of the elongated central pressing portion in opposite directions to thereby form a Z-shaped configuration. When assembled, the elongated central pressing portion of the linear-type locking device lodges in a heat sink, and the locking arms thereof are then resiliently deflected downwardly to engage with positioning means provided on a frame or socket to thereby secure the heat sink to a CPU. An example of a linear-type locking device is shown in U.S. Pat. No. 5,386,338. However, a linear-type locking device generally has a slim structure, it cannot firmly secure a heat sink to a CPU, especially nowadays the heat sink being made heavier and heavier aiming to obtain a high heat dissipating capacity.
In order to overcome the disadvantage of the above-mentioned linear-type locking devices, plate-type locking devices have been developed. An example of a plate-type locking device is shown in U.S. Pat. No. 6,118,661. The disclosed plate-type locking device has generally a M-shaped configuration and includes a V-shaped central pressing portion for pressing against a heat sink and a pair of locking feet extending downwardly from opposite ends of the V-shaped central pressing portion for respectively engaging with a pair of protrusions provided at a socket mounted on a printed circuit board (PCB). The plate-type locking device is integrally formed and therefore has a large rigidity, and accordingly, large force is needed to operate the plate-type locking device in assembly. When large force is applied, the plate-type locking device is prone to slide over the protrusions of the socket, which will possibly damage other electronic devices mounted on the PCB.